A boiler requires extremely pure water in order to avoid a plurality of different problems. Unfortunately water available for most boilers is not pure enough to avoid these problems. Untreated water would rapidly damage the boiler eventually destroying it.
Currently there are a variety of different physical and chemical treatments for boiler water. BOILER WATER TREATMENT an article from the magazine Power, June, 1987, p. S1-S16 describes many of these different treatments. Further, "Chemical Treatment Options For Steam Generation" in the same magazine February of 1982, p. 93-97 discusses similar treatments and solutions. Some of the problems defined by these papers are scale, pH, pitting by oxygen and carbonic acid formed from carbon dioxide.
Phosphates are typically used as an internal treatment for scale prevention in boilers. Basically this forms a sludge that is easily removed. Other scale preventers includes low molecular weight polymers generally in combination with phosphates and the like. Polymethacrylates and polyacrylates having molecular weights around 4500 have also been used for scale. These act not only to prevent scale formation but also in certain applications can act as descalants. Polymaleic acid is also employed.
Oxygen pitting is typically solved by removal of oxygen in the make-up water. A large amount of oxygen dissolved in water can be removed by physical treatment, dearation. Subsequent chemical treatment by oxygen scavengers is then required to remove the last traces of oxygen. There are several different oxygen scavengers. Hydrazine is a commonly employed scavenger. Unfortunately generated steam containing hydrazine is unsuitable for applications where the steam may contact food. Other less dangerous chemicals typically used include sulfites such as sodium sulfite and erythorbic acid. The use of this composition is disclosed for example in U.S. Pat. No. 4,419,327. It is also known to use ascorbic acid but this treatment is not commonly employed.
There are various volatile amines which have been used for condensate treatment. These include ammonium hydroxide which is incompatible with any kind of copper surface. Cyclohexylamine has been used but is not compatible with a highly alkaline carbonate system. Morpholine exhibits a low distribution ratio and would protect the short steam system however medium to long condensate lines would not be protected. Octadecylamine is a filming amine and diethylaminoethanol is another amine used to treat condensate systems.
Other chemicals used to treat boiler water include sodium hydroxide which increases alkalinity and precipitates magnesium, sodium carbonate which also increases alkalinity and precipitates calcium, and magnesium, chelants such as ethylenediaminetetraacetic acid, tannins, starches, lignins, carboxymethylcellulose which prevents feed line deposits, sodium nitrate which inhibits caustic embrittlement and antifoaming agents.
These many different chemical treatment agents are generally applied separately at separate locations along the boiler system. Incompatibility of concentrated solutions of these treatment agents has generally prevented formulation of all-in-one treatments which would be stored and shipped in concentrated form and applied at use dosages.